Hydrometallurgical recovery of Zn(II) and Mn(II) from alkaline batteries waste employing aqueous two-phase system

In this study, a greener method for the recovery of zinc and manganese from alkaline batteries waste was developed using Aqueous Two-Phase System (ATPS). ATPS is a liquid-liquid extraction technique. Zn(II) and Mn(II) were extracted using the diluted liquor from samples of spent alkaline batteries, and the experimental conditions were evaluated considering the effects of the following parameters: (i) nature and concentration of the extractants (1-(2-pyridyl-azo)-2-naphthol (PAN), (bis-4-trimethylpentyl) phosphinic acid (Cyanex 272), diphenylthiocarbazone (dithizone, C13H12N4S) and bis-(2-ethylhexyl) phosphoric acid (D2EHPA)); (ii) pH (3.00, 6.00 and 11.0), (iii) ATPS-forming electrolytes (Na2SO4, C6H5Na3O7 or C4H4Na2O6); (iv) ATPS-forming polymers (L35 and L64); and (v) tie-line length (TLL) and mass ratio between top and bottom phases (mTP/mBP). The recovery efficiency was evaluated using the extraction percentage (%E) and separation factor (SZn/Mn) between Zn(II) and Mn(II). The best conditions for selective extraction of the metal ions were achieved using an ATPS composed by L64 + Na2SO4 + H2O at pH = 3.00, TLL = 41.83% w/w and mTP/mBP = 1 using dithizone as the extracting agent and leach liquor with dilution factor equal to 10. This resulted in a value for separation factor of SZn/Mn = 1.2 × 106, in one extraction stage.